1. Field of the Invention
The present invention relates to a film deposition apparatus and a film deposition method for depositing a film on a substrate by carrying out plural cycles of supplying in turn at least two source gases to the substrate in order to form plural layers of a reaction product, and a storage medium storing a computer program for carrying out the film deposition method.
2. Description of the Related Art
As a film deposition technique in a semiconductor fabrication process, there has been known a so-called Atomic Layer Deposition (ALD) or Molecular Layer Deposition (MLD), in which a first reaction gas is adsorbed on a surface of a semiconductor wafer (referred to as a wafer hereinafter) under vacuum and then a second reaction gas is adsorbed on the surface of the wafer in order to form one or more atomic or molecular layers through reaction of the first and the second reaction gases on the surface of the wafer, and such an alternating adsorption of the gases is repeated plural times, thereby depositing a film on the wafer. This technique is advantageous in that the film thickness can be controlled at higher accuracy by the number of times of supplying in turn the gases, and in that the deposited film can have excellent uniformity over the wafer. Therefore, this deposition method is thought to be promising as a film deposition technique that can address further miniaturization of semiconductor devices.
Such a film deposition method may be preferably used, for example, for depositing a dielectric material to be used as a gate insulator. When silicon dioxide (SiO2) is deposited as the gate insulator, a bis (tertiary-butylamino) silane (BTBAS) gas or the like is used as a first reaction gas (source gas) and ozone gas or the like is used as a second gas (oxidation gas).
In order to carry out such a deposition method, use of a single-wafer deposition apparatus having a vacuum chamber and a shower head at a top center portion of the vacuum chamber and a deposition method using such an apparatus has been under consideration. In the deposition apparatus, the reaction gases are introduced into the chamber from the top center portion, and unreacted gases and by-products are evacuated from a bottom portion of the chamber. When such a deposition chamber is used, it takes a long time for a purge gas to purge the reaction gases, resulting in an extremely long process time because the number of cycles may reach several hundred. Therefore, a deposition method and apparatus that enable high throughput is desired.
Under these circumstances, film deposition apparatuses having a vacuum chamber and a turntable that holds plural wafers along a rotation direction have been proposed in order to carry out ALD or MLD. Specifically, such a deposition apparatus has plural process areas where corresponding reaction gases are supplied, the process areas being positioned away from one another along the rotation direction of the turntable, and a separation area including a separation gas supplying member for supplying a separation gas in areas between adjacent process areas along the rotation direction in order to separate the atmospheres of the process areas.
At the time of depositing films, the separation gas is supplied from the separation gas supplying member and spreads in both directions in relation to the rotation direction of the turntable. As a result, a separation area is created that impedes the reaction gases from being mixed. The reaction gases are evacuated along with the separation gas that has spread in both directions in relation to the rotation direction of the turntable from an evacuation port. While the reaction gases are supplied in the process areas and the separation gas is supplied in the separation area in such a manner, wafers placed on the turntable are repeatedly moved from one process area to the other process area by rotating the turntable, and thus the ALD or MLD is carried out. According to such a deposition apparatus, because gas purging in the process chamber is not necessary and a film can be concurrently deposited on plural wafers, high throughput is expected.
In the above deposition apparatus, if the reaction gases flow into the separation area and the reaction gases are mixed, normal film deposition becomes impossible. For example, no film may be deposited on the wafers, or film thickness may vary over the wafer. In order to avoid gas mixture of the reaction gases, the separation gas needs to be supplied at a high flow speed. To this end, it may be required to increase a flow rate of the separation gas. However, when the flow rate of the separation gas is increased, the separation gas flows into the process areas and dilutes the reaction gases, and thus the deposition efficiency may be reduced. In order to avoid such a problem, it may be advantageous to increase a gas evacuation amount from the evacuation port. However, this may increase an evacuation load of the evacuation apparatus such as a vacuum pump connected to the evacuation port.
Patent Document 1 listed below discloses a deposition apparatus whose process chamber has a shape of a flattened cylinder. The process chamber is divided into two half circle areas. Each area has an evacuation port provided to surround the area at the top portion of the corresponding area. In addition, the process chamber has a gas inlet port that introduces separation gas between the two areas along a diameter of the process chamber. With these configurations, while different reaction gases are supplied into the corresponding areas and evacuated from above by the corresponding evacuation ports, a turntable is rotated so that the wafers placed on the turntable can alternately pass through the two areas.
Patent Document 2 discloses a process chamber in which four wafers are placed on a wafer support member (rotation table) at equal angular intervals along a rotation direction of the wafer support member, first and second gas ejection nozzles are located along the rotation direction and oppose the wafer support member, and purge nozzles that are located between the first and the second gas ejection nozzles. In this process chamber, the wafer support member is horizontally rotated in order to deposit a film on the wafers.
However, these documents do not describe any configurations of reducing an amount of the separation gases, and thus the above problem cannot be solved by these documents.
Patent Document 3 (Patent Documents 4, 5) discloses a film deposition apparatus preferably used for an Atomic Layer CVD that causes plural gases to be alternately adsorbed on a target (a wafer). In this apparatus, a susceptor holding the wafer is rotated, while source gases and purge gases are supplied to the susceptor from above. Paragraphs 0023-0025 of the document describe partition walls that extend in a radial direction from a center of a chamber, and gas ejection holes that are formed in a bottom of the partition walls in order to supply the source gases or the purge gases. An inert gas as the purge gas is ejected from the gas ejection holes, thereby producing a gas curtain. However, this document does not show a technique reducing a flow rate of the purge gas.
Patent Document 1: U.S. Pat. No. 7,153,542 (FIGS. 6A, 6B)
Patent Document 2: Japanese Patent Application Laid-Open Publication No. 2001-254181 (FIGS. 1, 2)
Patent Document 3: Japanese Patent Application Laid-Open Publication No. 2007-247066 (paragraphs 0023 through 0025, 0058, FIGS. 12 and 18)
Patent Document 4: United States Patent Publication No. 2007/218701
Patent Document 5: United States Patent Publication No. 2007/218702